From patchwork Wed Jun 27 11:21:38 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chris Wilson X-Patchwork-Id: 10491157 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id C633160375 for ; Wed, 27 Jun 2018 11:21:56 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B3DBD289E0 for ; Wed, 27 Jun 2018 11:21:56 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id A6FA528BB8; Wed, 27 Jun 2018 11:21:56 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.2 required=2.0 tests=BAYES_00, MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED autolearn=ham version=3.3.1 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 48B80289E0 for ; Wed, 27 Jun 2018 11:21:56 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 67B3E6E898; Wed, 27 Jun 2018 11:21:55 +0000 (UTC) X-Original-To: intel-gfx@lists.freedesktop.org Delivered-To: intel-gfx@lists.freedesktop.org Received: from fireflyinternet.com (mail.fireflyinternet.com [109.228.58.192]) by gabe.freedesktop.org (Postfix) with ESMTPS id 627D86E898 for ; Wed, 27 Jun 2018 11:21:54 +0000 (UTC) X-Default-Received-SPF: pass (skip=forwardok (res=PASS)) x-ip-name=78.156.65.138; Received: from haswell.alporthouse.com (unverified [78.156.65.138]) by fireflyinternet.com (Firefly Internet (M1)) with ESMTP id 12174124-1500050 for multiple; Wed, 27 Jun 2018 12:21:41 +0100 Received: by haswell.alporthouse.com (sSMTP sendmail emulation); Wed, 27 Jun 2018 12:21:40 +0100 From: Chris Wilson To: intel-gfx@lists.freedesktop.org Date: Wed, 27 Jun 2018 12:21:38 +0100 Message-Id: <20180627112138.14273-1-chris@chris-wilson.co.uk> X-Mailer: git-send-email 2.18.0 In-Reply-To: <48daa46e-f7ca-c2c5-b849-2a9999cffe98@linux.intel.com> References: <48daa46e-f7ca-c2c5-b849-2a9999cffe98@linux.intel.com> X-Originating-IP: 78.156.65.138 X-Country: code=GB country="United Kingdom" ip=78.156.65.138 Subject: [Intel-gfx] [PATCH] drm/i915/execlists: Reset CSB write pointer after reset X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" X-Virus-Scanned: ClamAV using ClamSMTP On HW reset, the HW clears the write pointer (to 0). But since it also writes its first CSB entry to slot 0, we need to reset the write pointer back to the element before (so the first entry we read is 0). This is required for the next patch, where we trust the CSB completely! Signed-off-by: Chris Wilson Cc: Tvrtko Ursulin --- drivers/gpu/drm/i915/intel_lrc.c | 19 +++++++++++++++++-- 1 file changed, 17 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c index 368a8c74d11d..8b111a268697 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -884,6 +884,21 @@ static void reset_irq(struct intel_engine_cs *engine) clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted); } +static void reset_csb_pointers(struct intel_engine_execlists *execlists) +{ + /* + * After a reset, the HW starts writing into CSB entry [0]. We + * therefore have to set our HEAD pointer back one entry so that + * the *first* entry we check is entry 0. To complicate this further, + * as we don't wait for the first interrupt after reset, we have to + * fake the HW write to point back to the last entry so that our + * inline comparison of our cached head position against the last HW + * write works even before the first interrupt. + */ + execlists->csb_head = GEN8_CSB_ENTRIES - 1; + WRITE_ONCE(*execlists->csb_write, (GEN8_CSB_ENTRIES - 1) | 0xff << 16); +} + static void execlists_cancel_requests(struct intel_engine_cs *engine) { struct intel_engine_execlists * const execlists = &engine->execlists; @@ -1953,7 +1968,7 @@ static void execlists_reset(struct intel_engine_cs *engine, __unwind_incomplete_requests(engine); /* Following the reset, we need to reload the CSB read/write pointers */ - engine->execlists.csb_head = GEN8_CSB_ENTRIES - 1; + reset_csb_pointers(&engine->execlists); spin_unlock_irqrestore(&engine->timeline.lock, flags); @@ -2452,7 +2467,6 @@ static int logical_ring_init(struct intel_engine_cs *engine) upper_32_bits(ce->lrc_desc); } - execlists->csb_head = GEN8_CSB_ENTRIES - 1; execlists->csb_read = i915->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)); if (csb_force_mmio(i915)) { @@ -2467,6 +2481,7 @@ static int logical_ring_init(struct intel_engine_cs *engine) execlists->csb_write = &engine->status_page.page_addr[intel_hws_csb_write_index(i915)]; } + reset_csb_pointers(execlists); return 0;